Lubrication and sealing of well drilling bit



Jan. 24, 1967 K. H. swART ETAL 3,299,973

I LUBRICATION AND SEALING OF WELL DRILLING BIT Filed July 27. 1964 2Sheets-Sheet 1 FIG. l.

ATTORNEYS Jan. 24, 1967 K. H. SWART ETAL 3,299,973

LUBRICATION AND SEALING 0F WELL DRILLING BIT 2 Sheets-Sheet 2 FZUEMUIQEWE 332 INVENTORS KENNETH H. SWART BY WILLIAM P ROBINSON ATTORNEYSUnited States Patent 3,299,973 LUBRICATION AND SEALING 0F WELL DRILLINGBIT Kenneth H. Swart and William P. Robinson, Compton,

Califi, assignors to Smith Industries International, Inc.,

Compton, Califl, a corporation of California Filed July 27, 1964, Ser.No. 387,268 8 Claims. (Cl. 175-371) This invention relates toimprovements in well drilling bits, and particularly to that type ofwell drilling bit which employs roller cutters.

It has been proposed heretofore to supply the roller cutters of a welldrilling bit with a lubricant which will lubricate the bearings betweenthe cutter and the journal on which the cutter rotates and to provide aseal between the cutter and the body of the bit that will tend toconfine the lubricant within the cutter and prevent ingress ofdestructive materials to the bearings.

A primary object of the present invention is to provide an improved sealwhich is of extremely simple and durable construction which will preventingress of destructive materials and which will be effective regardlessof whether the cutter may be angularly displaced, radially displaced, oraxially displaced with respect to the journal.

Another object of the invention is to provide a seal which has theabove-mentioned characteristics and which can be used in a manner tofacilitate the assembly of the bit in the course of its construction.

Still another object of the invention is to provide a well drilling bitof the roller cutter type wherein a differential in hydrostatic pressureis caused to exist across the seal so that there will be a net effectivepressure on the exterior of the seal which constantly urges it intosealing engagement, thus assuring that ingress of destructive materialsto the hearing or bearings will be effectively prevented.

With the foregoing and other objects in view which will be made manifestin the following detailed description and specifically pointed out inthe appended claims, reference is had to the accompanying drawings foran illustrative embodiment of the invention, wherein:

FIGURE 1 is a partial view in vertical section through a portion of awell drilling bit embodying the present invention;

FIG. 2 is a partial view in vertical section illustrating the manner inwhich the bit embodying the present invention can be advantageouslyassembled; and

FIGS. 3, 4, 5, and 6 are partial views in section illustrating themanner in which the seal is effective in the event that the cutter isangularly displaced, radially displaced, or axially displaced withrespect to the journal on which it is rotatable.

Referring to the accompanying drawings wherein similar referencecharacters designate similar parts throughout, the improved welldrilling bit consists of a body 10, the upper portion of which is shapedto provide a threaded pin 11 providing for its engagement to the lowerend of a drill string. On this body there is formed a journal 12 onwhich a roller type cutter 13 is rotatably mounted. 14 indicates acirculation hole through which well drilling circulation fluid may bedischarged from the drill string in the vicinity of the cutter 13.

In conformity with conventional practice, there is a rolleranti-friction bearing 15 between the cutter and the journal near thepoint of connection between the journal and the body 10. Inwardly ofthis roller bearing there is a ball bearing 16, the balls of which arefed into their races formed on the journal and on the interior of thecutter 13 through a ball passage 17 that is subsequently closed by aball plug 18 welded in place as at 19. Friction-type bearings, bothradial and thrust, indicated at Patented Jan. 24, 1967 20 and 21respectively, may be provided between the inner end of the cutter andthe inner end of the journal and appropriate passages may be formed forconducting lubricant to the various bearings 15, 16, 20 and 21.

The above-described construction is more or less conventional in rollercutter-type well drilling bits but may be departed from insofar as thepresent invention is concerned.

An important part of the present invention relates to the establishmentof a seal between the outer side of the cutter 13 and the body 10 aroundthe base of the journal 12. To this end, a frusto-conical or inwardlytapering surface 22 is formed on the body 10 around the base of thejournal 12. This frusto-conical or tapering sur face tapers in adirection axially of the journal and toward the inner end of thejournal. Against this surface there is positioned in stretched conditionan elastic, endless ring 23. This ring may conform in its constructionto a conventional rubber O-ring being circular in plan and circular incross-section. As this endless elastic ring rest against the surface 22in a stressed or stretched condition it will continually tend tocontract against this tapered surface and will consequently beconstantly urged by its own self-exerted force against the counterboresurface 24 formed on the outer face of the cutter 13.

In order to lubricate the bearings between the cutter and the journal alubricant reservoir 25 is formed in the body 10 adjacent each journal.This lubricant reservoir has a lubricant confined therein by means of apiston 26 that may be sealed such as by an O-ring 27. The upper surfaceof this piston is exposed to the hydrostatic pressure in the well thatis accessible thereto through the opening 28 formed in the cap 29 thatconfines the piston in the lubricant reservoir. This cap may be weldedin place, such as by welds 30.

A compression spring 31 is disposed in the lubricant reservoir and iscompressed between the piston 26 and the plug 18. Lubricant in thelubricant reservoir can be expelled therefrom into the passages betweenthe cutter 13 and the journal to lubricate the various bearings. Thepressure within the cutter, however, is equal to the hydrostaticpressure existing on the exterior of the bit minus the elfectivepressure exerted by the compressed coil spring 31. Consequently, thepressure of the lubricant in the lubricant reservoir and in the passagesleading to the bearings will always be somewhat less than thehydrostatic pressure existing on the exterior of the bit. In thismanner, a differential pressure is caused to exist on opposite sides ofthe sealing ring 23. On the outer side of the sealing ring 23 thepressure exerted is that of the hydrostatic pressure that is present onthe exterior of the bit, which frequently is quite high, often severalthousand pounds per square inch. On the inner side of the sealing ring23 the pressure exerted by the lubricant is slightly less due to theforce exerted by the spring 31 on the underside of the piston 26. Thisnet effective pressure on the sealing ring 23 urging the sealing ringtoward the interior of the cutter cooperates with the self exertedcontractile force of the stretched sealing ring on the tapered surface22 to urge the sealing ring into sealing engagement with the rotarycutter 13.

The improved seal lends itself toward facilitating as sembly of the bit.Thus, as illustrated in FIG. 2, in the course of assembling the elementsof the bit the rollers of the roller bearing 15 may be assembled aroundthe journal 12. The sealing ring 23 can'then be stretched and appliedaround the rollers and allowed to contract thereon and assume a positionas illustrated in FIG. 2. Thereafter, the cutter 13 may be axiallyslipped onto the journal with the race on the cutter for the rollers 15serving to slip the sealing ring 23 axially off of the rollers.Thesealing ring will consequently hold the rollers in assembled positionwhile the cutter 13 is being applied. When the cutter shifts the sealingring 23 off of the rollers and onto the tapered surface 22 the ring maycontract further but even in its contractedpositi-on it is stillstretched or stressed.

As illustrated in FIG. 3, if the cutter becomes angularly displaced withrelation to the journal for any one of a number of different reasons,such as for example wear in the course of use the stretched sealing ringthat is continually contraction on the tapered surface and which issubjected to the differential in pressures merely accommodates oradjusts itself to these conditions. Thus, in FIG. 3, a slight angulardisplacement is shown wherein the left-hand side of the cutter is spacedfrom the wall of the body surrounding the tapered surface 22 to aconsiderable extent but the right-hand side is not. The sealing ringmerely adjusts itself to these conditions.

In FIG. 4, the cutter is illustrated as having been radially displacedwith respect to the journal and under these conditions the sealing ringmerely adjusts or accommodates itself to these conditions remaining insealing engagement with the cutter.

In FIGS. 5 and 6, two forms of axial displacement of the cutter wit-hrelation to the journal are illustrated. In FIG. 5, the cutter is shownas having been displaced toward the inner end of the journal and in FIG.6, the cutter is shown as having been displaced toward the outer end ofthe journal. Under both sets of conditions the sealing ring merelyconforms itself to the circumstances in which it finds itself and due toits self-exerted contractile effort on the tapered surface 22 coupledwith the differential in pressure existing thereon sealing engagement isconstantly maintained.

It will be appreciated that it is not necessary in all instances tocreate a differential in pressure across the sealing ring, such as bymeans of the spring-actuated piston 26. Without a spring-actuated pistonthe piston merely acts as a pressure equalizer to prevent fullhydrostatic pressure being applied across the seal. Without such adifferential in pressure the sealing ring may continue to functionsatisfactorily due to its stressed condition. The use of thedifferential pressures on opposite sides of the sealing ring ispreferred however, and the use of such pressures on other forms of sealscan be used to advantage. The simplicity of construction of the O-ringtype seal causes that type of seal to be preferred, particularly onaccount of its ability to accommodate itself or adjust itself to thevarious conditions that it may encounter as illustrated in FIGS. 3 to 6,inclusive.

It will be appreciated from the above-described construction that theimproved seal is very simple and is capable of being very economicallyemployed. Furthermore, the seal when applied facilitates greatly theholding of the roller bearing 15 in place while the cutter is beingapplied.

We claim:

1. In a roller cutter well drilling bit wherein a roller cutter ismounted for rotation on a journal on a bit body, sealing means betweenthe roller cutter and the bit body, and means for causing a differentialin hydrostatic pressure to exist between the exterior of the bit and theinterior of the cutter surrounding the journal when the bit is inoperation and surrounded by drilling fluid with the lesser pressure inthe interior of the cutter so that a net effective pressure will beapplied to the sealing means by the drilling fluid urging the sealingmeans toward the interior of the cutter.

2. In a roller cutter well dsrilling bit, a body part having a journaland a cutter part rotatably mounted thereon, one of said parts having anannular tapered surface tapering towrd the other and disposed adjacent aface on the other, and an annular elastic sealing ring stretched ontosaid surface on said part which by reason of its contraction will crowditself toward the other to form sealing engagement therewith, and meansfor causing a differential in hydrostatic pressure to exist between theexterior of the bit and the interior of the cutter part with the greaterpressure on the exterior of the bit and the lesser pressure on theinterior of the cutter when the bit is in operation and surrounded bydrilling fluid, which differential in pressure is effective on theexterior of the sealing ring to urge the sealing ring against thementioned face.

3. In a roller cutter well drilling bit, a body having a journal onwhich a roller cutter is rotatably mounted, said body presenting anannular surface tapering toward the cutter and disposed adjacent a facethereon, an endless elastic sealing ring disposed in stretched conditionon said surface and crowded toward the mentioned face on the cutter byits effort to contract, means for causing a differential in hydrostaticpressure to exist between the exterior of the bit and the interior ofthe cutter, and means including a spring-urged piston whose spring isarranged to oppose pressure existing on the exterior of the bit fortransmitting some of the hydrostatic pressure existing on the exteriorof the bit to the interior of the cutter so that the net effectivepressure on the ring will cooperate with its self-crowding to urge thering into sealing engagement with the mentioned face on the cutter.

4. In a roller cutter Well drilling bit, a body part having a journal onwhich a roller cutter part is rotatably mounted, an annular surface onone of said parts which is tapered in a direction axially of the journaland toward an adjacent face on the other of said parts, an endlesssealing ring on said surface in circumferentially stressed condition andconsequently self-crowded toward the mentioned'face on the other part tosealingly engage therewith, and means causing a hydrostatic pressuredifferential to exist on opposite sides of the sealing ring when the bitis in operation and surrounded by drilling fluid to urge the sealingring towards the said mentioned face on the other part.

5. In a roller cutter well drilling bit wherein there is a body having ajournal on which a cutter is rotatably mounted, an endless sealing ringbetween the body and the cutter, and means for causing a differential inhydrostatic pressures on opposite sides of the sealing ring with thegreater pressure on the exterior of the bit and the lesser pressure onthe interior of the cutter effective to urge the sealing ring toward thecutter.

6. In a roller cut-ter well drilling bit for operation in a drillingfluid under pressure, a body having a journal on which a roller cutteris rotatably mounted, said body presenting an annular tapered surfacetapering toward an adjacent face on the cutter, an endless elasticsealing ring disposed in stretched condition on said tapered surface andcrowded toward the mentioned face on the cutter by its effort tocontract, and means for producing fluid pressure in the cutter inwardlyof the sealing ring less than that of the drilling fluid on the exteriorof the cutter and which is effective on the exterior of the sealingring.

7. In a roller cutter well drilling bit for operation in a drillingfluid under pressure, a body having a journal on which a roller cutteris rotatably mounted, said body presenting an annular tapered surfacetapering toward an adjacent face on the cutter, an endless elasticsealing ring disposed in stretched condition on said tapered surface andcrowded toward the mentioned face on the cutter by its effort tocontract, means providing a passage in the body between the exterior ofthe body and the interior of the cutter inwardly of the sealing ring, aspring-urged piston in said passage, the spring of the piston beingarranged to oppose the transmission of drilling fluid pressure from theexterior of the body through said passage to the interior of the cutter,and said passage, between said piston and said sealing ring, beingadapted to hold fluid lubricant.

8. In a roller well drilling bit for operation in a drilling fluid underpressure, a body having a journal on which a roller cutter is rotatablymounted, an endless sealing ring on the body engageable with a face onthe cutter to seal therewith under the influence of greater pressure onthe exterior of the bit than in the interior of the cutter, there beinga fluid lubricant passage in the body leading from the exterior thereofto the interior of the cutter inwardly of the sealing ring, andspring-actuated means in said passage for partially transmitting fluidpressure from the exterior of the bit to the interior of the cutter, thespring being arranged to oppose the transmission of fluid pressurewhereby the pressure maintained in the interior of the cutter will beless than that on the exterior of the bit and the net effective pressureon the sealing ring will 'be effective to urge it into sealingengagement with the face on the cutter.

References Cited by the Examiner UNITED STATES PATENTS Scott 175228Green 3088.2 Derman 277-95 X Skupas 27795 X

2. IN A ROLLER CUTTER WELL DRILLING BIT, A BODY PART HAVING A JOURNALAND A CUTTER PART ROTATABLY MOUNTED THEREON, ONE OF SAID PARTS HAVING ANANNULAR TAPERED SURFACE TAPERING TOWARD THE OTHER AND DISPOSED ADJACENTA FACE ON THE OTHER, AND AN ANNULAR ELASTIC SEALING RING STRETCHED ONTOSAID SURFACE ON SAID PART WHICH BY REASON OF ITS CONTRACTION WILL CROWDITSELF TOWARD THE OTHER TO FORM SEALING ENGAGEMENT THEREWITH, AND MEANSFOR CAUSING A DIFFERENTIAL IN HYDROSTATIC PRESSURE TO EXIST BETWEEN THEEXTERIOR OF THE BIT AND THE INTERIOR OF THE CUTTER PART WITH THE GREATERPRESSURE ON THE EXTERIOR OF THE BIT AND THE LESSER PRESSURE